DESCRIPTION(Adapted from applicant's abstract): The guiding hypothesis of this work is that alterations in the conformation of the microtubule associated protein tau are an important part of a cascade of events that leads to cell death in Alzheimer's disease and certain other neurodegenerative diseases. Genetic studies of families with frontotemporal dementia with Parkinson's disease (FTDP) provide support for this hypothesis. In the next project period, further testing will be carried out by experimental work ranging from in vitro manipulation of tau protein conformation and phosphorylation, cell culture experiments with transfection of various tau constructs and examination of transgenic animals. Five specific aims are proposed: Aim #1. Two short amino acid sequences in tau have been identified as critical for formation of an abnormal conformation of tau, that is similar to that of tau present in the AD brain. Using recombinant tau constructs, structural requirements for generation of this conformation will be further explored. The effects of several point mutations and phosphorylation will also be examined. In Aim #2, the activity of these abnormal tau proteins will be investigated using assays of microtubule binding and promotion of tubulin assembly, to test the hypothesis that the abnormal tau is no longer a functional microtubule binding protein. In Aim #3, selected tau constructs will be transiently transfected into cultured cells to test the hypothesis that specific constructs are non-functional in a cellular environment. In Aim #4, a variety of mice into which normal and mutant human tau transgenes have been introduced will be examined, including unique lines which we will produce. Since the tau mutatons discovered in FTDP are dominant, the hypothesis that these mice will show neuronal degeneration seems reasonable. Aim #5. Using selected antibodies from a large panel of monoclonals to conformational and phosphoepitopes of tau, studies of human brain will continue to attempt to examine the relationship between certain phosphorylations and conformational changes in tau, especially focusing on early AD cases.